1/3/2012 11:43 AM PST

This has gotta hurt. Dr. Conrad Murray has been ordered to turn over the medical certificate that hangs on the wall of his medical office.

TMZ has just obtained documents filed by the Medical Board of California, notifying the incarcerated doc that his California medical license has been suspended -- something that automatically happens when someone is convicted of a felony and sent to the slammer.

The Med Board is giving Murray 15 days to turn over his medical certificate.

If the wall is too bare, he can always hang a picture of Michael Jackson ...